blk-throttle: Eliminate redundant checks for data direction

After calling throtl_peek_queued(), the data direction can be determined so
there is no need to call bio_data_dir() to check the direction again.

Signed-off-by: Tang Yizhou <yizhou.tang@shopee.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240123081248.3752878-1-yizhou.tang@shopee.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>